1. Field of the Invention
This invention relates to the continuous hot rolling of heated billets that are slit in the course of being processed into finished products such as bars and rods.
2. Description of the Prior Art
In a conventional continuous hot rolling mill, an exemplary rolling diagram of which is depicted in FIG. 1, a typical billet 10 is initially heated to a temperature of about 1050–1150° C. The billet is then rolled in a series of roll stands 1V-12H/V arranged along a pass line P1 into a first process section 12. As shown in FIG. 2A, the first process section 12 has laterally disposed segments 14 of equal cross sectional area joined by an intermediate first web 16.
With reference again to FIG. 1, at 18, the first web 16 is slit to separate the segments 14, which are then directed to separate pass lines P2 for continued rolling into second process sections 20 in roll stands 13H-16H/V. As shown in FIG. 2B, each of the second process sections also has laterally disposed segments 22 of equal cross sectional area joined by an intermediate second web 24.
At 26 as shown in FIG. 1, the second webs 24 are slit to separate the segments 22, which segments are then directed to separate pass line P3a–P3d for rolling into finished products 28 in some or all of the roll stands 17–24 of finishing blocks “M”.
Because the process sections 12 and 20 are slit into segments having equal cross sectional areas, the finishing blocks are each fed with the identical slit segments 22. This severely limits the range of products that can be produced by the mill with a given roll pass design and guide set up. By way of illustration, assume for example that the entering billet 10 measures 160×160 mm with a cross sectional area of 26,322 mm, that the slit segments 14 and 22 have respective cross sectional area of 32.4 mm2 and 15.6 mm2.
With reference to FIG. 3, and using the finishing block arranged on pass line P3a as an example, the following rolling sequences and resulting products are possible:
ROLLING SEQUENCEFINISH SIZE (DIAMETER)17-246.3mm17-228mm17-2010mm17-1812.5mm
In order to produce other products, the mill must be shut down while the roll passes are reconfigured and guides are changed.
A primary objective of the present invention is to substantially broaden the range of products that can be rolled simultaneously with a given roll pass configuration in a mill in which slitting is employed.
A companion objective of the present invention is to achieve the aforesaid broadening of the product range while also increasing the hourly production rate of the mill.